Inhaled nitric oxide (INO) will be evaluated as a potential therapy for term and near-term infants with hypoxic respiratory failure including infants with primary persistent pulmonary hypertension of the newborn (PPHN), meconium aspiration, sepsis/pneumonia, respiratory distress syndrome, suspected pulmonary hypoplasia, and congenital diaphragmatic hernia (CDH). Between June 1996 and November 1998, INO was used with all eligible infants in accordance to the recommendations of the Neonatal Inhaled Nitric Oxide Study (NINOS) performed by the NICHD Neonatal Research Network in conjunction with the Canadian Inhaled Nitric Oxide Study Group. In November 1998 eligible patients were enrolled into a similar randomized, controlled trial in which the benefits of early INO would be evaluated in infants with moderate respiratory failure. Infants who presented with severe respiratory failure would receive open lable INO treatment under the same IND. (This is a NICHD Neonatal Research Network Trial.)